The new nectarine tree ‘S 6816’ was developed by the Institut National de la Recherche Argonomique (INRA) at Angers, France, as part of a controlled breeding program. ‘S 6816’ was one of several seedlings resulting from a cross of [(Kiang-Si×Independence)×Summergrand]×Marsun (all unpatented). ‘S 6816’ was asexually propagated by budding at Angers, France, and has been observed to remain true to type over successive asexually propagated generations.